RF systems components are generally configured for a standardized characteristic impedance, enabling interconnection of the various systems components with reduced power losses.
Standardized characteristic impedances common in the RF industry include 50, 75, 110 and 300 Ohms. At microwave frequencies, the preferred characteristic impedance is 50 ohms. Therefore, a large number of microwave frequency RF devices such as transceivers, antennas, interconnecting transmission lines and other devices configured for in-line connection are configured for 50 ohm characteristic impedance.
Prior impedance matching adapters have applied a range of different electrical circuitry and/or apparatus to transform characteristic impedance, for example, between 50 and 75 ohms. RLC lumped element impedance transformers, such as wound ferrite toroids, may generate undesirable parasitic effects as operating frequencies increase, for example above 500 Mhz.
Another impedance matching solution is application of a load inline with the transmission line. Impedance transformers of this type may introduce an insertion loss that is unacceptably high.
The dimensions of microstrip transmission lines may be manipulated to form low loss impedance transformers. Multi-section impedance matching transformers such as Chebyshev ¼ wavelength, coaxial, microstrip or stripline transformers apply a series of transmission line width steps, each spaced ¼ wavelength apart along the transmission line. Passage along the transmission line through each step raises or lowers the characteristic impedance depending upon the direction of travel. Depending upon the desired operating frequency(s) and acceptable insertion loss levels, a series of steps separated by ¼ wavelength each, suitable to arrive at the desired characteristic impedance transformation, may require a transmission line of considerable length.
Cost of manufacture, including materials costs and labor, may be a significant factor in commercial success in the impedance adapter market.
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.